2-1/4" ID anti siphon device fits Freightliner models.   Easy to install, extremely secure and an effective solution to help prevent fuel theft.  A measurement of the ID of the fuel tank fill neck is always advised.   Made out of aluminum.   Guaranteed for the life of the fuel tank they are installed in.  They do not restrict fueling and there is no splash-back.  Made in the U.S.A. Sold individually.